BACKGROUND: Today, many healthcare or dementia organizations, clinicians, and companies emphasize the importance of detection of Alzheimer's disease in an early phase. This idea has gained considerable momentum due to the development of biomarkers, the recent FDA and EMA approval of three amyloid tracers, and the failure of a number of recent therapeutic trials conducted in the early dementia phase. On the one hand, an early etiological diagnosis can lead to early and moreefficacious intervention. On the other hand, it is questioned how early anetiological diagnosis is beneficial to the patient. Here we consider ethicalissues related to the process of biomarker testing and the impact on thediagnostic disclosure to patients with mild cognitive impairment due to prodromal Alzheimer's disease.METHODS: A systematic review of the theoretical bioethics literature wasperformed by using electronic databases. The review was limited to articles published in English between 2003 and 2016.RESULTS: A total of twenty articles were included in our effort to make ananalysis of the ethical challenges. One of the biggest challenges was theuncertainty and the predictive value of the biomarker-based diagnosis where patients can be amyloid positive without full certainty whether or when they will develop symptomatic decline due to Alzheimer's disease. Another challenge was the tension between the right to know versus the wish not to know, the limited efficacy of currently available treatment options, and the opportunities and consequences after receiving such an early diagnosis.CONCLUSION: Based on the results and the additional comments in the discussion, several unanswered questions emerged. Therefore, careful consideration of all these ethical issues is required before the disclosure of a biomarker-based diagnosis to the patient with mild cognitive impairment due to Alzheimer's disease.